The present invention relates to a diffusion bonding apparatus for pipes, more particularly a diffusion bonding apparatus for pipes capable of diffusion bonding a pipe that is supplied from above with a pipe that is placed in position therebelow by evenly pressing them against each other.
Conventionally, because of a superior quality in a bonded joint, various products are produced by using diffusion bonding. It is also expected that oil well pipes with bonded joint of a superior quality can be obtained, if the diffusion bonding is used for production of oil well pipes.
Then, as shown in FIG. 7, according to an apparatus A' for achieving diffusion bonding by vertically holding a pipe (lower pipe) P1 to be bonded, supplying the other pipe (upper pipe) P2 to be bonded therewith downward from above in the vertical direction, allowing an end surface of the upper pipe P2 to be pressed against an end surface of the lower pipe P1 that is held vertically therebelow, then heating the relevant joint for diffusion bonding them, it is considered that such pipe as an oil well pipe extending as far as several kilometers after bonding can be produced. An apparatus of above constitution is herein referred to as a vertical diffusion bonding apparatus A'.
However, in a microscopic view of an end of the pipes P1, P2, as shown in FIG. 8, it is very rare that surfaces to be bonded are exactly at a right angle with respect to a longitudinal center of the pipes P1, P2. Therefore, when the upper pipe P2 is pressed against the lower pipe P1, the pressing force is concentrated in a part of the pipes P1, P2, and the entire area of surfaces to be bonded cannot be evenly pressed against each other by a desired force. As a result, because a desired degree of tightness cannot be achieved, gaps are present in some areas. Then, due to lack of pressing force in such areas, the bonded joint is accordingly reduced in strength after bonding.
The invention has been achieved in view of such problems of the prior art, and it is an object of the invention to provide a diffusion bonding apparatus for pipes capable of achieving diffusion bonding by evenly pressing pipes against each other even when the perpendicularity of end surfaces of the pipes to be bonded with respect to a longitudinal center thereof is somehow low in accuracy.